I have a Sega Saturn that was given to me. No controllers, cables, games, anything. I've been trying to get it working to no avail. I have an AV cable and a power cord and a controller. When I power the device on, the left direction on the controller doesn't work. I've replaced the carbon pads inside, as well as the controller board in the Saturn to no avail. I don't have any other accessories.Any ideas?

Can I control the system functions if I plug the controller into the second port?

I just tried it on my US model 2 and it works fine with port 2. I can press Start at the boot screen and if there's no disc in it'll take me to the player. All functions work as expected through controller port 2.

I agree with this. Definitely try cleaning the board. I had two SNES controllers where the Start button barely worked, I really had to jam on it. Took them apart and there was some sort of dark substance on them. Took a toothbrush to it and cleaned it up with some Isopropyl alcohol and it worked good as new.